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The IP Network Address Translator (NAT) (RFC1631)

IP.com Disclosure Number: IPCOM000002467D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2019-Feb-12
Document File: 10 page(s) / 14K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K. Egevang: AUTHOR [+1]

Related Documents

10.17487/RFC1631: DOI

Abstract

This memo proposes another short-term solution, address reuse, that complements CIDR or even makes it unnecessary. The address reuse solution is to place Network Address Translators (NAT) at the borders of stub domains. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 15% of the total text.

Network Working Group K. Egevang Request for Comments: 1631 Cray Communications Category: Informational P. Francis NTT May 1994

The IP Network Address Translator (NAT)

Status of this Memo

This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Abstract

The two most compelling problems facing the IP Internet are IP address depletion and scaling in routing. Long-term and short-term solutions to these problems are being developed. The short-term solution is CIDR (Classless InterDomain Routing). The long-term solutions consist of various proposals for new internet protocols with larger addresses.

It is possible that CIDR will not be adequate to maintain the IP Internet until the long-term solutions are in place. This memo proposes another short-term solution, address reuse, that complements CIDR or even makes it unnecessary. The address reuse solution is to place Network Address Translators (NAT) at the borders of stub domains. Each NAT box has a table consisting of pairs of local IP addresses and globally unique addresses. The IP addresses inside the stub domain are not globally unique. They are reused in other domains, thus solving the address depletion problem. The globally unique IP addresses are assigned according to current CIDR address allocation schemes. CIDR solves the scaling problem. The main advantage of NAT is that it can be installed without changes to routers or hosts. This memo presents a preliminary design for NAT, and discusses its pros and cons.

Acknowledgments

This memo is based on a paper by Paul Francis (formerly Tsuchiya) and Tony Eng, published in Computer Communication Review, January 1993. Paul had the concept of address reuse from Van Jacobson.

Kjeld Borch Egevang edited the paper to produce this memo and introduced adjustment of sequence-numbers for FTP. Thanks to Jacob Michael Christensen for his comments on the idea and text (we thought

Egevang & Francis [Page 1]

RFC 1631 Network Address Translator May 1994

for a long time, we were the only ones who had had the idea).

1. Introduction

The two most compelling problems facing the IP Internet are IP address depletion and scaling in routing. Long-term and short-term solutions to these problems are being developed. The short-term solution is CIDR (Classless InterDomain Routing) [2]. The long-term solutions consist of various proposals for new internet protocols with larger addresses.

Until the long-term solutions are ready an easy way to hold down the demand for IP addresses is through address reuse. This solution takes advantage of the fact that a very small percentage of hosts in a stub domain are communicating outside of the domain at any given time. (A stub domain is a domain, such as a corporate network, that only handles traffic originated or destined to hosts in the domain). Indeed, many (if not most) hosts never communicate outside of their stub domain. Because o...

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